Diminishing returns – maybe…

Here’s something you don’t hear a teacher say often: “Some of my students need to start studying less and enjoying life more!” Yes, I actually said that, eyes focused vacuously in middle-distance, in handing back the mock exams. It’s like hearing “No, duct tape won’t fix that!” in Missouri or “Pass me the pate” in the Stallone household.

I meant it. I still do to a certain extent but I’ve toned down the correlation aspect as you shall see below. Anyhow, in going through the mock results, the economist in me reared its ugly head and I started to discern a pattern. It seemed that the very pressured students who were doing huge amounts of after-school study courses were performing at levels clearly beneath there inherent skills, intellect and ambition.

Now, there turns out to be a bit of a ‘weeding-out’ problem here since there are other variables at play that influence grades. In other words, I once again raise a cautionary hand in going through the murky waters of correlation and causality – the statistics above do not tell the whole story. It’s a bit like looking at the SR Phillips curve and saying “Aha! Rising unemployment causes falling inflation rates.” Well, no. Instead both unemployment and inflation are instead caused by changes in AS/AD. The correlation between the two is largely spurious in fact.

Teaching here in Shanghai as I do, our student body is predominantly Asian and are here for a few years of high school before returning home to go to university. It turns out that many of these expatriate Asian students don’t really need the IB grades in the first place: instead, they need to pass a university entrance exam given by their home school boards in their home language. We see thus that the IB incentive goes down while the home-system incentive is strengthened.

One can therefore see that it really isn’t ‘increased afternoon class activity’ that causes IB grades to go down but primarily the case that home-country demands on university entrance incentivize students to re-allocate their energy towards afternoon classes rather than homework. We don’t really see diminishing returns, in any true sense of the term, since the afternoon classes are not ‘producing’ the same goods, e.g. rather than economics, students are learning their home language and culture.